The present invention relates to a device for removing dust coming from air from a work processing machine and more particularly from a floor sanding machine, comprising a dust separator arranged in the flow path in the form of a centrifugal or cyclone separator, which has a lower dust outlet opening from which the separated dust drops along a descent path to a connection port for connection with a dust collecting container, and an upper air outlet opening for the outlet of the air freed of dust, and with a filter device arranged in the flow path downstream from the dust separator for filtering out the remaining dust, which has an annular configuration and surrounds the dust separator with the formation of filter chamber, which is connected with the air outlet opening of the dust separator.
It is more particularly in the case of wood working machines and specifically in the case of machines for sanding floors that it is conventional to draw off the dust produced by means of a blower from the respective point of work processing and to supply the air containing the dust to a dust filter bag, whose wall material retains the dust so that the dust will collect in the filter bag, whereas the cleaned air will flow off through the material of the wall. This method of dealing with dust has various disadvantages:
With an increase in the height of filling of the filter bag there is an decrease in the free surface area of its wall material and consequently of the area available for the escape of the air to the outside. This is responsible for a corresponding drop in the suction performance with the result that the filter bag has to be replaced by a fresh one after a comparatively short period of time when it is only partly full. Such filter bags are however comparatively expensive, and there is the further aspect labor being necessary for changing of the bag.
Furthermore the filter bag material, even above the level of filling, is heavily laden with dust, this meaning that on changing the filter bag a cloud of dust will emerge from it if it is held in the hand and thereby unavoidably bent.
Departing from this normally adopted practical method of operating it is more advantageous to utilize a device of the type initially mentioned as disclosed in the German patent publication 1,165,390 B or the German patent publication 896,285 C. In the case of such a device the dust separator arranged upstream from the filter device serves to remove the greater part of the dust from the air flow. This dust then directly goes into the sealed off dust collector container, which, because it does not have any filter function and exclusively functions to collect the dust, may consist of dust-tight, smooth material, with the result that it is externally not dusty or dust laden and internally as well above the filling level practically no dust adheres. Such a container may essentially be completely filled so that it accordingly has to be less frequently replaced or emptied.
These known devices are however, like other known equipment, disadvantageous to the extent that during the course of time filtered off residual dust collects in the filter chamber and reduces the filtering area available. Therefore it is necessary for the filter device to be taken to pieces from time to time for removal of the accumulated residual dust. This is an inconvenience and leads to the escape of dust into the environment.